With the growth of video-capable mobile devices, such as smartphones, tablets, and wearable devices, users' media viewing habits have gradually shifted out of the living room, and into the outside world—into every corner and crevice where these devices can be used. Similarly, this shift has displaced the traditional television set—a bulky screen designed to be mounted semi-permanently in a single place, such as on a wall or on a flat surface—in favor of small, portable screens that can be viewed in virtually any position, and in virtually any orientation.
Such mobile devices place new demands on video content. One such demand relates to the aspect ratio (e.g., the ratio of a display width to a display height) of the video content. Under desired viewing conditions, a native aspect ratio of a video asset (e.g., a source file containing video content) matches the aspect ratio of the display on which the video asset is presented. For example, when viewing a video asset on a display having a 16:9 aspect ratio, it is desirable that the video asset itself have a 16:9 aspect ratio. If the video asset has an aspect ratio that differs from the aspect ratio of the display, one of two conventional solutions can be used to format the video asset for the display: either the video asset can be cropped to fit the display (e.g., via “pan and scan” techniques); or the video asset can be “letterboxed” by adding dummy content (e.g., black bars) to fill the regions of the display unoccupied by the video asset. Neither solution is desirable: cropping the video asset results in the cropped content being unviewable on the display (which can affect the viewer's understanding or appreciation of the video asset); and letterboxing the video asset results in regions of the display being effectively unused (which can impair visibility, especially on mobile devices with limited display space).
A preferred solution is to anticipate the aspect ratio of the display on which video content will be viewed, and to provide to the display a video asset that matches that aspect ratio. But this approach is frustrated by mobile device displays that change aspect ratios as the user changes the orientation of the device. For instance, a display may be in a “portrait” mode (e.g., in which the aspect ratio is less than unity) when a device is held upright, but may shift to a “landscape” mode (e.g., in which the aspect ratio is greater than unity) when the device is rotated 90 degrees to the left or the right. A solution is needed for seamlessly switching between aspect ratios of video content without resorting to cropping or letterboxing techniques.
Further, users of mobile devices demand that video content be data-efficient: that is, that the video content respect the limited data storage capacity of many mobile devices, and the cost and overhead of downloading large files on consumer data plans; and that it accommodate the high latency, low bandwidth network conditions in which mobile devices may operate. The present disclosure describes such one or more solutions, which improve on conventional approaches by providing a data-efficient mechanism for quickly and seamlessly changing an aspect ratio of video content on a mobile device display.